Preserve provenance through pointer offsetting

src/mem/slab.h

@@ -43,8 +43,7 @@ namespace snmalloc
       void* head = meta.head;
 
       assert(rsize == sizeclass_to_size(meta.sizeclass));
-      meta.debug_slab_invariant(this);
-      assert(sl.get_head() == (SlabLink*)((size_t)this + meta.link));
+      assert(sl.get_head() == (SlabLink*)pointer_offset(this, meta.link));
       assert(!meta.is_full());
 
       void* p = nullptr;

src/test/func/memory/memory.cc

@@ -173,7 +173,7 @@ void test_external_pointer()
 
     for (size_t offset = 0; offset < size; offset += 17)
     {
-      void* p2 = (void*)((size_t)p1 + offset);
+      void* p2 = pointer_offset(p1, offset);
       void* p3 = Alloc::external_pointer(p2);
       void* p4 = Alloc::external_pointer<End>(p2);
       UNUSED(p3);

src/test/perf/external_pointer/externalpointer.cc

@@ -72,8 +72,8 @@ namespace test
         size_t* external_ptr = objects[oid];
         size_t size = *external_ptr;
         size_t offset = (size >> 4) * (rand & 15);
-        size_t interior_ptr = ((size_t)external_ptr) + offset;
-        void* calced_external = Alloc::external_pointer((void*)interior_ptr);
+        void* interior_ptr = pointer_offset(external_ptr, offset);
+        void* calced_external = Alloc::external_pointer(interior_ptr);
         if (calced_external != external_ptr)
           abort();
       }